Voltage stability in bulk power networks has been a big research topic in the past years since, and still the threat of Blackouts drive the need of new and better indicators to maintain a secure electrical power delivery to consumers.
Transmission networks today have to meet high demand and transmission needs to be increased on existing power grids without high investments. Additionally building new transfer lines is not always possible due to regulations by law or nature conservation. Power generation is more often far away from large consumers. This leads to more and more power systems operating more often and for longer time close to voltage stability limits. Power grids have to be more efficient, still they are expected to deliver reliable energy. Panning a power system needs to compromise between reliability and outage cost.
A heavily loaded power system is more vulnerable to disturbances than a non-stressed system. Already small disturbances, which had no severe effect since, can cause a system collapse on these stressed power systems. Power system instability may cause a blackout with high impact on economy but also on civilization, which is becoming more and more dependent on electricity.
A high number of examples for big blackouts exist, where widespread disruptions have happened due to interconnected power systems designed for improved availability of supply. Even after short disturbances in some cases the restarting process could take several hours for industrial companies.
In my thesis I reviewed the indices designed for voltage stability assessment. Afterwards, I conducted simulations to show at what extent power systems are exposed to voltage collapse. I used Power World software to do simulations on a 9 bus IEEE test system. Simulation results reveal which busbars represent the weak points in the grid.